I plan to analyze the genetic control of contact chemoreception, responses to chemicals in solution, in Drosophila by characterizing behavioral mutants. In preliminary studies, I have isolated 12 gustatory (gus) mutants which are indifferent or attracted to NaCl or quinine, stimuli avoided by normal Drosophila males. For the mutations that are known to be heat- or cold-sensitive, I will define the temperature-sensitive period, the stage of development during which a gus gene is active. This will provide information about when parts of the nervous system involved in chemotaxis differentiate. To identify parts of the nervous system which function during the performance of chemotactic behavior, I will analyze internally marked genetic mosaics in which a gus mutation is expressed in some tissues and not in others to see where the mutant gene acts to cause abnormal behavior. I will also ask whether mosaics expressing a mutation which disrupts acetylcholine metabolism perform normal chemotaxis, in an effort to identify cholinergic pathways which are involved in chemosensory behavior. In addition, I will attempt to isolate additional NaCl and quinine mutants as well as mutants with abnormal responses to the sugar fucose, which is attractive to wild-type flies. I will observe the behavior of each new mutant in various assays to determine the extent of its abnormalities. The behavior tests will reveal (1) whether a mutation affects responses to attractants, repellents, or both; (2) whether it perturbs fast and slow responses to chemical stimuli; and (3) whether it affects the behavior of larvae as well as adults. I will also ask whether any of the gustatory mutants have other behavioral defects, such as olfactory or visual deficits, abnormal locomotion, or aberrant courtship.